Inductive Power Transfer with Inductive Power Transfer Pad

ABSTRACT

An inductive power transfer pad for inductive power transfer to a vehicle includes a stationary part and a movable part, wherein the movable part comprises a primary winding structure for generating a magnetic or electromagnetic field while an electric current flows through windings of the primary winding structure, wherein the inductive power transfer pad comprises at least one actuator for actuating motion of the movable part, wherein the movable part is movable at least into a first direction by the at least one actuator so as to move between a retracted state and an extended state, wherein the inductive power transfer pad comprises a heating for heating the inductive power transfer pad.

The invention relates to an inductive power transfer pad and a systemfor inductive power transfer, in particular to a vehicle. Furthermore,the invention relates to a method of operating an inductive powertransfer pad.

Electric vehicles, in particular a track-bound vehicle, and/or a roadautomobile, can be operated by energy which is transferred by means ofan inductive power transfer. Such a vehicle may comprise a circuitarrangement, which can be a traction system or a part of a tractionsystem of the vehicle, comprising a receiving device adapted to receivea magnetic field or an electromagnetic field and to produce an electriccurrent by magnetic induction. Furthermore, such a vehicle can comprisea rectifier adapted to convert an alternating current (AC) produced bythe receiving device to a direct current (DC). The DC can be used tocharge a traction battery or to operate an electric machine. In thelatter case, the DC can be converted into an AC by means of an inverter.

The inductive power transfer is performed using two sets of windingstructures. A first set (primary winding structure) is fixed, such asinstalled on the ground and can be fed by a wayside power converter(WPC). The second set of windings is installed on the vehicle. Forexample, the second set of windings (secondary winding structure) can beattached to the vehicle, e.g. underneath the vehicle, in the case oftrams under some of its wagons. For an automobile it can be attached tothe vehicle chassis. The second set of windings or, generally, thesecondary side arrangement is often referred to as pick-up or receiver.The first set of windings and the second set of windings form a highfrequency transformer to transfer electric energy to the vehicle byconverting it into field energy on the primary side, transferring thefield energy and converting it back into electric energy on thesecondary side. This can be done in a static state (when there is nomovement of the vehicle) and in a dynamic state (when the vehiclemoves). Besides stationary primary side units movable units are alsoknown which comprise a movable part comprising the primary windingstructure.

U.S. Pat. No. 5,654,621 discloses an inductive transmitter having aprimary element and a secondary element which is attached to thevehicle, wherein the primary element is power driven to move in allthree spatial coordinates with a predetermined spatial area.

DE 10 2010 042395 A1 discloses a system for inductive charging of abattery of a vehicle, wherein a primary coil is automatically placeable.

DE 10 2007 033654 A1 discloses a base unit with a driving means toreduce a distance between a primary conductor and a secondary coil.

US 2010/0235006 A1 discloses a movable automated charging apparatuscomprising a base, a scissor lift, a pedestal, a joint and a charger.The charger is configured to mate with a vehicle receptacle physicallyor via proximity.

The inductive power transfer pad according to the present inventioncomprises a stationary part and a movable part. The movable partcomprises a primary winding structure for generating a magnetic orelectromagnetic field while an electric current flows through windingsof the structure. At least one actuator actuates motion of the movablepart, wherein the movable part is movable at least into a firstdirection by the at least one actuator so as to move between a retractedstate and an extended state. The invention is not limited to pads havingan extended state in which the movable part has always the sameposition. Rather, as for example mentioned above in connection with U.S.Pat. No. 5,654,621, the movable part may be moved in all three spatialdirections. As a result, the extended state may include a multiplicityof positions of the movable part relative to the stationary part. On theother hand, it is preferred that the movable part is always in the sameposition and orientation with respect to the stationary part, when themovable part is in the retracted state.

Typically, the stationary part comprises operating devices, which areelectric and/or electronic devices adapted to operate the primarywinding structure so that the primary winding structure generates themagnetic or electromagnetic field. The operating devices areelectrically connected to the primary winding structure and produce heatduring operation. Examples of the operating devices are semiconductorswitches, such as IGBTs, of a converter for converting a direct currentinto an alternating current which flows through the primary windingstructure during operation. Alternatively, the converter may convert analternating current having a first, smaller frequency into analternating current having a second, higher frequency. Another exampleof the operating devices are capacitors for compensating an inductanceor inductances of the primary winding structure. In particular, thereactance of the arrangement shall be reduced by the capacitor(s).

During operation of the primary winding structure, the heat produced bythe operating devices is to be transported away from the operatingdevices. Otherwise, they may malfunction or may be damaged. In addition,the operating temperature of the operating devices may be limited by amaximum value for smooth operation.

Furthermore, rough operating conditions of the inductive power transferpad are to be taken into account. Dirt and liquids may drop from avehicle which is to be provided with energy by the inductive powertransfer pad. Therefore, such foreign matters may cover the surface ofthe pad and may deteriorate the heat transport to the environment.

It is an object of a first aspect of the invention to provide aninductive power transfer pad having a stationary part and a movable partcomprising a primary winding structure, wherein the heat transport fromthe operating devices to the environment shall be maintained despiteouter influences, such as foreign matters. It is a further object of thefirst aspect of the invention to provide a corresponding systemcomprising the inductive power transfer pad and other system components,such as a control device for controlling the operation of the inductivepower transfer pad and/or a secondary side receiving device (pickup)which may be attached to a vehicle. Still a further object of the firstaspect of the invention is to provide a corresponding method ofoperating an inductive power transfer pad.

According to a basic idea of the first aspect of the invention, thestationary part of the pad comprises a cooling device which is thermallycoupled to the operating devices and which is adapted to transfer heatto an environment of the inductive power transfer pad. Such a coolingdevice improves the heat transport to the environment.

In order to protect the cooling device from outer influences while themovable part is in the retracted state, the cooling device is covered bythe movable part in the retracted state and the movable part uncoversthe cooling device while being moved into the extended state. Therefore,the cooling device is not only protected in the retracted state, butheat transfer to the environment is improved in the extended state.

Therefore, the following is provided: An inductive power transfer pad,in particular a transfer pad of a system for inductive power transfer toa vehicle, comprising a stationary part and a movable part, wherein themovable part comprises a primary winding structure for generating amagnetic or electromagnetic field while an electric current flowsthrough windings of the structure, wherein the inductive power transferpad comprises at least one actuator for actuating motion of the movablepart, wherein the movable part is movable at least into a firstdirection by the at least one actuator so as to move between a retractedstate and an extended state, wherein

-   -   the stationary part comprises operating devices, which are        electric and/or electronic devices adapted to operate the        primary winding structure so that the primary winding structure        generates the magnetic or electromagnetic field, wherein the        operating devices are electrically connected to the primary        winding structure and produce heat during operation,    -   the stationary part comprises a cooling device which is        thermally coupled to the operating devices and is adapted to        transfer heat to an environment of the inductive power transfer        pad,    -   the cooling device is covered by the movable part in the        retracted state and the movable part uncovers the cooling device        while being moved into the extended state.

In addition, a corresponding method is proposed of operating aninductive power transfer pad, in particular a transfer pad of a systemfor inductive power transfer to a vehicle, comprising a stationary partand a movable part, wherein the movable part comprises a primary windingstructure which is operated to generate a magnetic or electromagneticfield by conducting an electric current through windings of thestructure, wherein an actuator of the inductive power transfer padactuates motion of the movable part, so that the movable part is movedat least into a first direction and so that the movable part is movedbetween a retracted state and an extended state, wherein

-   -   operating devices of the stationary part, which are electrically        connected to the primary winding structure, operate the primary        winding structure so that the primary winding structure        generates the magnetic or electromagnetic field and produce heat        during operation,    -   a cooling device of the stationary part, which is thermally        coupled to the operating devices, is used to transfer heat to an        environment of the inductive power transfer pad,    -   the cooling device is covered by the movable part in the        retracted state and the movable part uncovers the cooling device        while being moved into the extended state.

A preferred embodiment of the cooling devices comprises a heat sink. Inparticular, the heat sink may comprise ribs and/or fins. More generallyspeaking, the heat sink may be formed so as to have an increased surfacecompared to a device of the same volume and in particular of the samebasic form (such as cuboid). In particular, the heat sink has aplurality of projections projecting from its surface.

By using a heat sink, the heat is efficiently transferred from the heatsink to the air. In case of the projections (e.g. ribs and/or fins), theheat is transferred from the heat sink to the environment via acorrespondingly shaped surface.

The cooling device may comprise more than one heat sink. In this case,it is preferred that each heat sink is covered by the movable part inthe retracted state and is uncovered if the movable part moves into theextended state.

The movable part may comprise separate elements, which are notnecessarily moved in the same manner. For example, the elementcomprising the primary winding structure may be lifted in the firstdirection while an additional cover element which covers the coolingdevice moves in a different direction and/or is tilted away from thecooling device. Preferably, the motion of different elements of themovable part is kinematically coupled. For example, the same actuator orthe same arrangement of coupled actuators may be used to actuate thecoupled motion.

According to a preferred embodiment, at least one of the operatingdevices is located in a housing, wherein an outer shell of the housingis made of a first material. The cooling device is located outside ofthe housing. During operation of the operating devices, heat isconducted from at least one of the operating devices to the coolingdevice via a heat conducting material extending through the outer shellof the housing, wherein the heat conducting material has a higher heatconductivity than the first material. For example, the first material isa plastic material and is preferably electrically insulating. The heatconducting material may be a metal, such as aluminum or copper, having ahigh heat conductivity or may be another material of high heatconductivity. The outer shell including the heat duct realized by theheat conducting material that extends through the outer shell preferablyforms a liquid-tight housing of the housed operating device(s).

In particular, the cooling device may be placed sideways of theoperating device in a direction transverse to the first direction intowhich the movable part can be moved into the extended state. Inparticular, the cooling device may be placed in a recess of thestationary part and the movable part may partially fill the recess inthe retracted state. The cooling device or a part of the cooling devicemay be placed in a remaining part of the recess. Preferably, a baseplate, sidewalls of the recess and the movable part may completely coverthe inner volume of the recess in the retracted state. This is also thepreferred embodiment if there is no cooling device or if there is nocooling device within the recess.

Since the cooling device is placed sideways of the operating device andsince the movable part is movable into the first direction transverse tothe direction connecting the operating device and the cooling device, anoverlap or projection (in particular of a lid) of the movable device maycover the cooling device in the retracted state. It is not necessarythat the covering section of the movable part contacts the coolingdevice in the retracted state, although this is possible. The overlap orprojection may or may not comprise a section or sections of the windingsof the primary winding structure. In the preferred embodiment, a housing(in particular the lid) of the movable part includes the completeprimary winding structure except the supply lines.

In particular, the first direction is the vertical direction and avehicle may be positioned above the inductive power transfer pad whilebeing provided with energy by the pad. It is preferred that the movablepart covers the cooling device at least in the first direction.

According to a second aspect of the invention, which can be combinedwith any other aspect of the invention or can be realized separately,the inductive power transfer pad comprises a cleaning device integratedin the inductive power transfer pad and adapted to remove foreignmatters (such as dirt, particles or liquid substances or combinationsthereof) from a space between the stationary part and the movable part.According to a corresponding method of operating the IPT pad, thecleaning device removes the foreign matters from the space.

In particular, the space is enclosed or at least partially enclosed bythe combination of the movable part and the stationary part, when themovable part is in the retracted state. In contrast, the space is notenclosed or enclosed to a lesser extent, if the movable part is in theextended state. This means that the space becomes exposed to possiblyentering foreign matters, if the movable part is moved from theretracted state to the extended state.

Due to the integrated cleaning device, the foreign matters are removed(or at least partially removed) from the space. Therefore, the IPT pad,a corresponding IPT system comprising the IPT pad and a correspondingoperating method solve the underlying problem that foreign matter mayintrude into the space while exposed to the environment.

Preferably, the cleaning device is automatically operated to remove theforeign matters from the space while the movable part moves from theextended state into the retracted state. This has the advantage that thespace is cleaned immediately before it is again protected to a higherextent when the movable part reaches the retracted state.

According to a specific embodiment, the cleaning device comprisesbellows (which may be the protective bellows described below) having anexpandable air volume with at least one air outlet adapted to direct anair blast to at least a part of the space between the stationary partand the movable part. The expandable air volume is inflated while themovable part moves from the retracted state into the extended state andis deflated while the movable part moves from the extended state intothe retracted state.

This is one embodiment which uses the motion of the movable part fromthe extended state into the retracted state to clean the space. Anotheroption which can be realized in addition or alternatively, is that thecleaning devices comprises a cleaning element (such as a brush) attachedto the movable part or to the actuator and arranged to wipe off theforeign matters from a surface of the stationary part and/or from theactuator. According to corresponding methods of operating the IPT padthe cleaning device blasts off and/or wipes off the foreign matters.Similarly to the embodiment using the air blast, the embodiment whichincludes wiping off the foreign matters (i.e. removes the foreignmatters mechanically) is not restricted to using the motion of themovable part from the extended state into the retracted state, althoughusing this motion is the preferred embodiment. In any case, using thismotion has the advantage that no additional actuator is required forperforming the cleaning.

According to an embodiment of the bellows, the expandable air volumeoccupies an area between the movable part and the stationary part.Further details are described below with respect to the protectivebellows. In case of the protective bellows, at least a part of theactuator is located in the expandable air volume. Therefore, this partof the actuator can be cooled by the air entering the air volume whilethe movable part is moved from the retracted state into the extendedstate. At least some of the heated air is blown out of (removed from)the air volume later, when the movable part moves back into theretracted state.

According to a preferred embodiment, the expandable air volume has anair inlet which is positioned closer to the movable part than to thestationary part. In particular, the air inlet may be located close tothe underside of the movable part (e.g. the housing which comprises theprimary winding structure) where it is likely that the air is notcontaminated. In particular, the air volume delimited by the bellows maybe covered by the housing of the movable part, wherein the housingprojects from the air volume sideways in a direction transverse to thefirst direction. In this manner, the area where the air inlet is locatedis additionally protected by the projection from contaminations in formof foreign matters.

In addition or alternatively, at least one air outlet of the expandableair volume is located closer to the stationary part than to the movablepart. Preferably, the at least one air outlet is positioned near by thespace which is to be cleaned from foreign matters. However, it is alsopossible that an air duct is connected to the air outlet and guides andoptionally redirects air from the air outlet to the space which is to becleaned.

A preferred object which is to be cleaned and is therefore located inthe space between the stationary part and the movable part is thecooling device of the first aspect of the invention. In particular,space portions in between ribs or fins of the cooling device may becontaminated with foreign matters and this will deteriorate the heattransfer from the cooling device to the surrounding air. Blowing aironto the cooling device cleans the cooling device from the foreignmatters and, in addition, increases the heat transfer from the coolingdevice to the surrounding air. Preferably, the air blast is directed insuch a manner that air flows in the longitudinal direction of spaces inbetween ribs or fins of the cooling device.

Optionally, the air inlet and/or the air outlet of the expandable airvolume can be provided with a one-way valve, such as a flap orcombination of flaps.

The bellows may be made of thin sheet-like, in particular flexibleplastic.

A third aspect of the invention, which can be combined with any otheraspect of the invention or can be realized separately, is based on theunderlying problem that the function of the IPT pad may be obstructed byice and snow. In particular, the movable part or any element of theactuator may freeze to the stationary part. Therefore, it is proposedthat the IPT pad comprises a heating for heating the IPT pad. Inparticular, before the movable part is moved from the retracted stateinto the extended state, the heating is operated. This will melt any icewhich obstructs the motion of the movable part.

In particular, the heating is an additional heating other than operatingdevices which are used to operate the primary winding structure in orderto generate the magnetic or electromagnetic field. In particular, anadditional electric heating (such as a heating comprising at least oneheating wire) is provided.

Preferably, the heating is located at a gap or at a boundary surface ofthe stationary part on one side and the movable part on the other side,when the movable part is in the retracted state. When moving the movablepart into the extended state, the gap will be increased or the movablepart will lose contact to the stationary part at the boundary surface,respectively. In any case, ice in the gap or at the boundary surface canbe removed (in particular melted).

In particular, the IPT pad is adapted to operate the heating while themovable part is in the retracted state and the primary winding structureis not operated. Operating the heating in particular prepares operatingthe actuator in order to bring the movable part in the extended statewhere the primary winding structure is to be operated. On the otherhand, it is also possible in some situations to operate the primarywinding structure in the retracted state. In this case, it might not benecessary to operate the additional heating, since motion of the movablepart is not required and since the primary winding structure may produceheat during operation which may also melt ice.

Preferably, the heating is only operated if the temperature of the pador in the environment is below a threshold value, such as 0° C.

According to another aspect which may be a sub-aspect of the thirdaspect of the invention, the underlying problem shall be solved that inparticular the stationary part and the actuator (in particular themovable elements of the actuator) shall be protected from liquids, suchas water.

In particular in the case that the stationary part defines a volumewhich is occupied by the movable part in the retracted state, and thatthe stationary part comprises a delimitation (such as the base plate)limiting the volume at its bottom, the delimitation may be provided withat least one opening (in particular a through-hole) adapted to drainliquids from the volume to an environment of the inductive powertransfer pad. Therefore, liquids and in particular melted ice can bedrained from the volume through the at least one opening in thedelimitation to the environment.

The term “pad” is used in this description for a device that comprisesthe stationary part and the movable part. For this reason, “pad” is notlimited to a monolithic block. Rather, “pad” is a common expression inthe technical field of IPT systems for the unit which comprises theprimary winding structure and optionally operating device for operatingthe primary winding structure.

As mentioned above, an inductive power transfer pad, in particular atransfer pad of a system for inductive power transfer to a vehicle, isproposed. The inductive power transfer pad (IPT pad) may be part of aprimary side unit or arrangement of a system for inductive powertransfer.

Furthermore, the power transfer pad comprises at least one actuator,wherein the movable part is movable at least into a first (in particularthe vertical) direction by the at least one actuator. In the context ofthis invention, the term “actuator” can denote the entity of allcomponents or elements by which the motion of the movable part iseffected.

The term “actuator” can thus comprise at least one force generatingactuating device and at least one coupling device for mechanicallycoupling the actuating device and the movable part and/or at least oneguide for guiding the movement of the movable part. The coupling devicemay be designed to transform motion generated by the actuating deviceinto motion of the movable part.

The movable part is movable between a retracted state and an extendedstate.

In the retracted state, the movable part, in particular a lower surfaceof the movable part, may have no distance or a minimum possible distancein the first direction of the stationary part, in particular of amounting portion of the stationary part of the IPT pad. Correspondingly,in the extended state, the distance of the movable part of the mountingportion can be a larger distance and in particular the maximum possibledistance which can be achieved by the actuator. The mounting portion (inparticular a base plate) can be used to mount the IPT pad to asupporting structure, in particular a surface of a route. The retractedstate and the extended state with the maximum possible distance canoptionally be defined by mechanical elements, e.g. stop elements and/orby the design of the actuator.

The first direction can be oriented parallel to a main propagationdirection of the electromagnetic field generated by the primary windingstructure during operation. In particular, the first direction can beoriented perpendicularly to a surface of the mounting portion (inparticular the base plate) of the IPT pad or a surface to which the IPTpad is connected, such as the ground.

In the retracted state, the upper surface of the movable part can belocated within the same plane as an upper surface of a portion (e.g. ahousing of the operating devices) of the stationary part.

The movable part may comprise a housing in which the primary windingstructure is arranged. Further, the movable part can comprise at leastone connecting terminal for a power connection of the primary windingstructure and the operating devices, e.g. an inverter, which can bearranged in the stationary part.

The movable part may comprise at least one object detection device,preferably housed by the same housing as the primary winding structure.In particular, the object detection device can detect a foreign object,in particular a metal object, and/or a vehicle within a charging volumeof the IPT pad. In particular, the object detection device can detect ormonitor a moving object, such as the vehicle to be charged.

At least one object detection device may comprise at least one inductivesensing system, wherein the inductive sensing system may comprise one ormultiple detection winding(s). Multiple detection windings can bearranged in an array structure wherein the array structure covers acharging surface of the power transfer pad. Therefore, an active(including field generation) or passive detection can be performed. Inthe case of an active detection, one or more excitation winding(s) canbe used. An active object detection can be performed by monitoringproperties of an excitation field generated by the excitationwinding(s). In the case of a passive detection, only one or more passivewinding(s) are used. A passive object detection can be performed bymonitoring properties of the passive winding(s), in particular aninductance. At least one object detection device (in the stationary partor the movable part) may comprise an RFID (radio frequencyidentification) unit. Using the RFID unit, a vehicle and, if applicable,a position of a vehicle with respect to the power transfer pad can bedetected.

Alternatively or in addition, the object detection device may perform animage-based object detection, which may comprise an image capturingdevice, such as a camera.

More generally speaking, the stationary part and/or the movable part,may comprise a vehicle detection system. The vehicle detection systemmay comprise at least one sensor and an evaluation unit for evaluatingoutput signals of the at least one sensor. The vehicle detection systemcan detect the presence of a vehicle in the surrounding of the IPT pad.For example, the vehicle detection system comprises an inductive sensor(e.g. a coil) and/or a capacitive sensor for detecting a vehicle.

The stationary part may comprise a DC connecting terminal and/or an ACconnecting terminal and may comprise optionally at least one currentconverter (e.g. AC/AC or DC/AC) comprising an input side which iselectrically coupled to the connecting terminal and an output sideelectrically coupled to the primary winding structure.

As mentioned before, the stationary part can comprise a housing. Theconverter can be arranged within the housing. In particular, theconverter may be arranged within an inner volume of the housing of thestationary part. The housing of the stationary part may be a part of alarger housing of the IPT pad.

For example, the IPT pad can be installed in a vehicle hall or car portof a private property or in a public parking area for automobiles,wherein the IPT pad can be connected via the connecting terminal to ahousehold electric network (generally an AC network) or a battery packproviding DC battery voltage with an arbitrary output voltage level.Generally speaking, the IPT pad can be installed on the ground such thata vehicle can be positioned above the IPT pad.

In particular, the IPT pad may be designed such that a power in therange of 3 kW to 20 kW can be transferred to e.g. a vehicle comprising acorresponding receiving device which can be also referred to as apick-up. An amplitude of an input voltage at the connecting terminal maybe 230V and an input current may be in the range of 16 A. This allowsfor transferring power in the range of 3 kW to 7 kW to a pick-up on asecondary side of an IPT system. Alternatively, the amplitude of theinput voltage may be 460V (or any other voltage) and the input currentmay be in the range of 32A, for example. This allows transferring powerof approximately 20 kW to a pick-up.

Optionally, the stationary part comprises a control unit for controllingan operation of the converter. The control unit may be arranged withinthe housing of the stationary part.

In particular, the power transfer pad, e.g. the stationary part and/orthe movable part, may comprise at least one guiding arrangement forguiding a magnetic flux (i.e. a magnetic field shaping arrangement) ofthe magnetic or electromagnetic field which is generated by the primarywinding structure. In particular, the power transfer pad can comprise aferrite arrangement, wherein the ferrite arrangement can e.g. compriseone or more ferrite bars or slab.

Preferably, the stationary part and/or the movable part, comprise(s) acompensating unit for compensating an inductance of a primary windingstructure. The compensating unit can e.g. comprise one or morecompensating capacitors which may be electrically connected in series tophase lines of the primary winding structure.

Furthermore, the IPT pad or a device connected to the IPT pad (such as awall-mounted device) may comprise a human-machine-interface (HMI) and/ora signal transmitting and receiving device. The HMI allows for providingan input to e.g. the control unit which controls the operation of theinverter. The HMI may comprise a monitor and/or a display which displaysinformation on a status of the IPT pad, e.g. if a charging process inprogress, to a user. In addition, the IPT pad may comprise an inputdevice, such as a touch-sensitive display and/or a keyboard. The signaltransmitting and receiving means may be designed to transmit a signaland/or data between a vehicle and the IPT pad.

The primary winding structure may have any configuration which cangenerate a magnetic or electromagnetic field. In particular, windings ofthe primary winding structure may form at least one coil and/or may havea meandering course. The primary winding structure may be a one-phase ormulti-phase structure.

Preferably, the stationary part and/or the movable part comprise(s) ashielding element, such as a metal shield. The shielding element shieldsan external area of the IPT pad from a field generated by the primarywinding structure. For example, a base plate of the stationary partand/or of the movable part may comprise a metal plate extending in thetwo directions perpendicular to the first direction.

According to a specific embodiment, the coupling device comprises ascissor gear, in particular a scissor lift in case of the firstdirection being the vertical direction. The movable part can bemechanically connected to one side of the scissor gear and thestationary part (in particular a base plate) to the opposite side.Thereby, the scissor gear moves the movable part in the first direction.

More generally speaking, the actuator may comprise a lever mechanism formoving the movable part in the first direction if operated by theactuating device. Alternatively or in addition, the actuating device maycomprise a piston-/cylinder unit (hydraulic or pneumatic), a linearmotor and/or an electromotor coupled to a worm-drive.

Optionally, the movable part can be movable in at least one lateraldirection in addition to the first direction. The lateral direction istransverse (in particular perpendicular) to the first direction. Thefirst and the lateral direction may define a plane which is parallel toan upper surface of the movable part. In particular, the movable partmay be movable so that a component of the motion extends in the firstdirection and, at the same time, a component of the motion extends inthe lateral direction.

In particular, the IPT pad may comprise protective bellows forprotecting at least a part of the actuator. In particular, at least apart and preferably all elements of the actuator can be arranged in aninner volume of the protective bellows. Therefore, foreign matter isblocked from entering the inner volume and any person nearby the pad isprotected to be hurt by interfering with the actuator. The movable part,in particular a housing of the primary winding structure, may form acover of the protective bellows and in this case may delimit its innervolume. The stationary part, in particular a base plate, may form acover of the protective bellows and delimits in this case its innervolume at the side opposite to the cover formed by the movable part. Thebellows may extend around and delimit the inner volume along the fourlateral sides of the inner volume.

Alternatively or in addition, the movable part is rotatable. Inparticular, the movable part can be rotated about an axis in the firstdirection and/or in the lateral direction which extends perpendicularlyto the first direction. Therefore, the orientation of the primarywinding structure relative to the secondary winding structure can beadjusted and power transfer can be enhanced.

The invention also relates to an inductive power transfer system (IPTsystem), in particular for an inductive energy transfer to a vehicle.The IPT system comprises the IPT pad according to one of the embodimentsdescribed in this description. Furthermore, the IPT system comprises atleast one receiving device (pick-up) for receiving a magnetic or anelectromagnetic field generated by the primary winding structure of theIPT pad. Furthermore, the invention comprises a method of operating thesystem.

Examples of the invention will be described with reference to theattached figures which show:

FIG. 1 a schematic side view of an inductive power transfer system,

FIG. 2 a perspective view on an inductive power transfer pad in aretracted state,

FIG. 3 a perspective view on the inductive power transfer pad shown inFIG. 2 in an extended state,

FIG. 4 a perspective view on another inductive power transfer pad in anextended state,

FIG. 5 another perspective view on the inductive power transfer padshown in FIG. 4,

FIG. 6 a perspective view on jet another inductive power transfer padand

FIG. 7 a perspective view on a jack-like lifting device.

FIG. 1 shows a schematic side view of an inductive power transfer systemcomprising an inductive power transfer pad 1 (IPT pad 1) having astationary part 2 and a movable part 3. Solid lines indicate the movablepart 3 in a retracted state and dashed lines show the movable part 3 inan extended state closer to a receiving device 11 mounted to theunderside of a vehicle 43. The power transfer pad 1 rests on groundsurface 7 which may be a driving surface for the vehicle 43. In theembodiment shown, the movable part 3 consists of a plate member 4 towhich an actuator 44 is attached for lifting and lowering the movablepart 3 in the vertical direction.

Within the plate member 4, a primary winding structure 6 is arranged.Optionally, at least a part of a foreign object and/or vehicle detectionsystem (not shown) can be arranged within the plate member 4.

The stationary part 2 comprises a housing 10 which forms acircumferential edge together with other peripheral elements 45 of thestationary part 2. For illustration purposes, the peripheral element inthe foreground of FIG. 1 is broken away. By the circumferential edge arecess 9 is defined, wherein the movable part 3 is at least partlylocated within the recess 9 in the retracted state. The actuator 44 isalso located within the recess 9 in a space between the movable part 3and the base plate 49 of the stationary part 2.

FIG. 1 also shows an operating device 38 for operating the primarywinding structure 6, thereby generating the magnetic or electromagneticfield. The operating device 38 is thermally coupled with a coolingdevice 31 in the recess 9 via a heat conducting material 39 whichextends from the operating device 38 through the outer shell of thehousing 10 to the cooling device 31. This improves heat transfer fromthe operating device 38 to the environment via the cooling device 31 inthe extended state of the movable part 3. The cooling device 31 has aheat sink comprising ribs 32 in order to increase the surface andtherefore the heat transfer to the environment.

A control device 12, which may be mounted to a wall (not shown), isconnected to electric and/or electronic devices within the housing 10via a cable 47.

FIG. 2 shows a perspective view of an inductive power transfer pad, suchas the IPT pad 1 of FIG. 1, with a plate member 4 of the movable part 3in the retracted state while it is received by the recess 9. Thestationary part 2 has a housing 10 for housing elements such as theoperating device 38 shown in FIG. 1. The other peripheral elements 45,which define the recess 9 together with the housing 10, are completelyshown in the figure. An upper surface of the housing 10 of thestationary part 2 is arranged within the same plane as the upper surface6 of the plate member 4 of the movable part 3.

A connecting terminal 13 for a connecting cable (such as the cable 47 ofFIG. 1) is located on the side of the housing 10. In this manner, theelectric and/or electronic components (such as components of a DC/ACinverter) within the housing 10 can be connected to external elements orunits of the system, such as the control device 12 shown in FIG. 1. Thehousing 10 may also comprise a controller (not shown) for controllingthe actuator (such as the actuator 44 schematically shown in FIG. 1)which actuates motion of the movable part 3. In addition, compensatingelements (not shown) for compensating an inductance of a primary windingstructure (not shown) can be arranged within the housing 10.

In this manner, the housing 10 protects the elements (such as theoperating devices) arranged within the housing 10 of the stationary part2 even if the movable part 3 is moved out of the recess 9 into theextended state.

FIG. 3 shows a perspective view of the IPT 1 shown in FIG. 2. Anactuating device of the actuator for actuating motion of the movablepart 3 can be arranged within the recess 9. The plate member 4 comprisescan another recess on its bottom side, wherein this recess is designedand arranged such that the actuating device is received by the recess inthe retracted state of the movable part 3. Further coupling means of theactuator arrangement couple the actuating device to the movable part 3,namely to a lifting mechanism of the movable part 3. In the exampleshown in FIG. 3, the lifting mechanism comprises four motion guides 17(e.g. guide rails), wherein the motion guides 17 may be formed by thesidewalls 18 of the recess 9. The motion guides are inclined and extendupwards. At least one element (not shown, for example a bearing element)of the movable part 3 may engage (e.g. project into) each of the motionguides, so that motion of the bearing elements and thereby the movablepart 3 is guided while the lifting mechanism is operated. If theactuating device exerts a force in a horizontal direction x onto themovable part 3, it moves along the motion guide upwards and is therebylifted. The lifting motion may be limited by a stop element, such as theend of the motion guides (e.g. guide rails). There are through-holes 35in the bottom section of the sidewall 18 which enable liquids from theinterior to be drained to the environment.

FIG. 4 shows a perspective view of another embodiment of an IPT pad. Thesame reference numerals are used for the same or functionally same partsand elements as in the other figures. Again, a movable part 3 comprisesa plate member 4 with an upper surface 6. The movable part is connectedto a lifting mechanism designed as a scissor lift 19 (see also theenlarged view of FIG. 5 with some parts being broken away, namely theleft section of the bellows 5, the left sidewall and the upper half ofthe front sidewall). The lifting mechanism is arranged within protectivebellows 5. In FIG. 4, an extended state of the movable part 3 is shown.

In FIGS. 4 and 5, cooling devices 31 a, 31 b in the form of ribbed heatsinks are shown next to (and preferably in contact with) the housing 10.As shown in FIG. 5, operating devices 38 a, 38 b can be located withinthe housing 10. Preferably, they at least one of the operating devices38 b is connected to the neighbouring cooling device 31 a via a heatconducting material as schematically shown in FIG. 1.

FIG. 5 shows another perspective view of the power transfer pad 1 shownin FIG. 4. In particular, a scissor lift 19 is visible which provides apart of the lifting mechanism. The scissor lift 19 is actuated by anactuating device 14 which is arranged within the recess 9 of the IPT pad1. A power cable 20 connects the primary winding structure (not shown)integrated in the plate member 4 with the operating devices 38, inparticular with the AC side of an inverter. By means of the scissor lift19, the movable part 3 can be lifted and lowered in the verticaldirection z.

At the bottom of the sidewall 18 on the right hand side of FIG. 5, thereis one of several possible drain holes 35 for draining liquids from thebottom of the recess 9 to the outside of the pad.

Generally speaking, drain holes in the stationary part of an IPT padenable the user or engineer to clean the pad with water or otherliquids. Preferably, all liquid-sensitive components are encapsulated,such as by the housing of the movable part or of the stationary part.

As schematically shown at the edge of the housing 10, the IPT pad 1comprises a heating 36 for heating the IPT pad 1. The heating extendsalong a surface of the housing which delimits a gap to the plate member4 of the movable part (in the retracted state). The same or anadditional heating may extend along a gap between the sidewalls 18 ofthe stationary part and the plate member 4. Alternatively, the primarywinding structure 6 may be used as a heating for melting ice in betweenthe stationary part and the movable part.

FIG. 6 shows a perspective view of another embodiment of an IPT pad. Aplate member (similar to the plate member shown in FIGS. 1 to 5) whichcomprises the primary winding structure is removed for illustrationpurposes. In FIG. 6, the movable part 3 comprises an air lift 21,wherein a translation stage 22 is arranged on an upper end of the airlift 21. The translation stage 22 is designed and arranged such that atranslational movement can be performed in a lateral directions x, y,wherein a plane spanned by the lateral direction x and the lateraldirection y is parallel to an upper surface 6 of the plate member 4. Theplate member 4 is mechanically connected to the translational stage 22.The air lift 21 comprises protective bellows 5 in the same manner as inFIG. 4.

Instead of an air lift 21, a scissor lift 19 (see FIG. 5) can be used inorder to move the movable part 3 in the vertical direction z.

The IPT pad shown in any of the figures may further comprise a safetymechanism for avoiding uncontrolled motion, in particular unwantedlowering, of the movable part 3. The safety mechanism can e.g. comprisea spring element and/or a damping element which is arranged between themovable part 3, in particular the plate member 4, and the stationarypart 2, in particular the base plate 49. For example, if the powersupply of the actuator fails, the movable part can be lowered in acontrolled manner.

Optionally, the IPT pad comprises a force sensor for sensing a forceacting on the movable part 3, in particular on the plate member 4. Inparticular, if the sensed force exceeds a predetermined threshold value,the movement of the movable part 3 can be stopped. This reduces thelikelihood of objects or limbs being pinched above or below the movablepart 3 during lifting or lowering. In addition to or alternative to aforce sensor, other object detection means can be used in order todetect objects within the motion range of the movable part 3.

FIG. 7 shows a partial perspective view of the embodiment shown in FIG.5. However, a part of the sidewall which is completely broken away inFIG. 5 is shown in FIG. 7, namely the part of which belongs to thehousing 10. In addition, the bellows 5 are shown almost completely,except for a corner section at the corner between the two sides shown inthe foreground of the figure. The missing corner section gives aninsight in the inner volume of the bellows 5 where the scissor lift islocated.

The bellows 5 comprise air inlet holes 52 at their top end which islocated at the underside of the plate member 4. The air inlet holes 52are located under a projection of the plate member 4 projecting beyondthe bellows 5 in horizontal (lateral) direction. When the movable partis lifted, the inner volume inside the bellows 5 is expanded (inflated)and air is sucked into the inner volume through the air inlet holes 52.

In addition, the bellows 5 comprise air outlet holes 51 located at theirbottom end. When the movable part is lowered, the inner volume insidethe bellows 5 is deflated and air blast out of the inner volume throughthe air inlet holes 52. The two air outlet holes 51 shown in FIG. 7 arelocated nearby and oriented towards the cooling device 31 a. Therefore,air is blown onto the cooling device 31 a and it is cleaned from foreignmatters.

FIG. 7 also shows a specific embodiment of a drain hole arrangement. Thedrain holes 35 shown are located in the sidewall of the housing 10.Preferably, there is a canal from the recess 9 connecting the drainholes 35 shown with the interior of the recess 9. In this manner, thedrainage capacity is increased. Additional drain holes can be located inthe side walls of the recess 9.

1-13. (canceled)
 14. An inductive power transfer pad for inductive powertransfer to a vehicle, comprising a stationary part and a movable part,wherein the movable part comprises a primary winding structure forgenerating a magnetic or electromagnetic field while an electric currentflows through windings of the primary winding structure, wherein theinductive power transfer pad comprises at least one actuator foractuating motion of the movable part, wherein the movable part ismovable at least into a first direction by the at least one actuator soas to move between a retracted state and an extended state, wherein theinductive power transfer pad comprises a heating for heating theinductive power transfer pad.
 15. The inductive power transfer pad ofclaim 14, wherein the heating is an additional heating other thanoperating devices, which are electric and/or electronic devices adaptedto operate the primary winding structure so that the primary windingstructure generates the magnetic or electromagnetic field.
 16. Theinductive power transfer pad of claim 14, wherein adapted to operate theheating while the movable part is in the retracted state and the primarywinding structure is not operated.
 17. The inductive power transfer padof claim 14, wherein the stationary part defines a volume which isoccupied by the movable part in the retracted state, wherein thestationary part comprises a delimitation limiting the volume at itsbottom and wherein the delimitation comprises at least one openingadapted to drain liquids from the volume to an environment of theinductive power transfer pad. 18-30. (canceled)
 31. A method ofoperating an inductive power transfer pad for inductive power transferto a vehicle, comprising a stationary part and a movable part, whereinthe movable part comprises a primary winding structure which is operatedto generate a magnetic or electromagnetic field by conducting anelectric current through windings of the primary winding structure,wherein an actuator of the inductive power transfer pad actuates motionof the movable part, so that the movable part is moved at least into afirst direction and so that the movable part is moved between aretracted state and an extended state, the method comprising: heating,by a heating, the inductive power transfer pad.
 32. The method of claim31, the method further comprising generating, by the primary windingstructure, the magnetic or electromagnetic field, wherein the heating isan additional heating other than operating devices, which are electricand/or electronic devices adapted to operate the primary windingstructure.
 33. The method of claim 31, the method further comprising:operating, by the heating, while the movable part is in the retractedstate and while the primary winding structure is not operated.
 34. Themethod of claim 31, the method further comprising defining, by thestationary part, a volume occupied by the movable part in the retractedstate, and draining liquids from the volume through at least one openingin a delimitation of the volume at its bottom to an environment of theinductive power transfer pad.